[Solved] How to align bullet to gun?

Newbie & Debugging Questions
#1 
       So I got my bullets spawning in the center of my character according to where it pointing right? Now I cant figure out how the diddly to align it not in the center. I want the bullets to spawn in front of my gun that is offset a bit. Changing anything in this formula shifts the location of the radius as a whole.

@Override
	public void fireWeapon() {
		float radians =  (float) Math.toRadians(playerMaster.getDirection());
		float gunPosX =  (float) (32 * Math.cos(radians) + weaponPosition.x + 32);
		float gunPosY =  (float) (32 * Math.sin(radians) + weaponPosition.y + 32);

		bulletList.add(new Bullet(gunPosX, gunPosY, playerMaster.getDirection(), playerMaster));
	}

If you could please explain the math that would be awesome, thank you.

#2

Can you do

bulletList.add(new Bullet(gunPosX + offset, gunPosY + offset, playerMaster.getDirection(), playerMaster));

where offset is the amount you need to offset it from where it is now? You might need to do a check to determine which direction the weapon is facing, and offset accordingly.

#3

I can do that, but that shifts the whole radius aswell. Maybe I have to do that but also do more Cosine and Sine math?

#4

Can you just do a check for the change in radius and then change the gunposx, y accordingly? sorry I dont know much about sine and cosine.

#5

The problem is I don’t know much about trigonometry either. Lmao.

#6 

	Vector bullet_spawn_location = new Vector(10, 0, 0);
	bullet_spawn_location = orientation_quaternion.asMatrix().multiply(bullet_spawn_location);

	Bullet bullet = new Bullet(bullet_spawn_location.x +player_location_x, bullet_spawn_location.y+ player_location_y, bullet_spawn_location.z + player_location_z, orientation_quaternion);

This is in 3D but im sure you get the gist.

#7

Currently, you are always rotating the point (1, 0) around a circle with radius 32.
Look at this “how to rotate a vector in 2D using an angle” formula (the two equations under “So the coordinates (x’,y’) of the point (x,y) after rotation are”). You want to do exactly this computation.

#8

I’ve tried all night to figure out what the diddly that formula means and I’m trying to implement it, but I still keep on just resizing the radius of the circular. With this code it makes a sort of asteroid orbit shape.

@Override
	public void fireWeapon() {
		float radians =  (float) Math.toRadians(playerMaster.getDirection());
		float gunPosX =  weaponPosition.x;
		float gunPosY =  weaponPosition.y;
		gunPosX += 62 * Math.cos(radians) - 20 * Math.sin(radians);
		gunPosY += 62 * Math.sin(radians) + 20 * Math.cos(radians);
				

		bulletList.add(new Bullet(gunPosX, gunPosY, playerMaster.getDirection(), playerMaster));
	}
#9

That formula gives you the new coordinates (x’, y’) of a 2D point (x, y) when you rotate that point around the origin (0, 0) through the given angle.
Think about what you want to rotate. It should be (x, y) = (weaponPosition.x, weaponPosition.y), when the following assumptions hold:

  • the origin (0, 0) of your model coordinates is the center of your player/model
  • (weaponPosition.x, weaponPosition.y) is expressed in model coordinates relative to that origin
  • when you rotate the player/model, then it also rotates about its own origin (0, 0)

Probably upload a drawing of your problem to an image hosting platform and reference it here, so that we can give you the exact formula you need.

#10

---------------------> the origin (0, 0) of your model coordinates is the center of your player/model <--------------------------

This is what’s done goofed me up. I appreciate your help a helluva lot, thank you. New Code that werks (weaponPosition.x + 32 is my center).

@Override
	public void fireWeapon() {
		float radians =  (float) Math.toRadians(playerMaster.getDirection());
		float gunPosX =  (float) ((float) weaponPosition.x + 32 +(30 * Math.cos(radians) - (-12) * Math.sin(radians)));
		float gunPosY =  (float) ((float) weaponPosition.y + 32 +(30 * Math.sin(radians) + (-12) * Math.cos(radians)));
				

		bulletList.add(new Bullet(gunPosX, gunPosY, playerMaster.getDirection(), playerMaster));
	}